The Blue Button API allows Medicare beneficiaries to access their health data through applications and services using standards-based APIs. The API is built on FHIR and provides access to claims data for 38 million Medicare beneficiaries from the past three years. It utilizes OAuth for authorization and integrates with MyMedicare.gov. The API provides a way for patients to take ownership of their health data and connect it to tools they trust, while building on open source solutions and industry standards to position CMS as a leader in health data interoperability.